The present invention relates to a method and apparatus for transmitting a signal through a power magnetic structure, such as the power transformer in a DC-DC converter.
In power circuitry, it is often required to isolate control signals as well as to isolate the output power from the input power. The power transformer that is found in many power circuits accomplishes the latter objective. However, isolating the control signals has generally required an additional isolation device, such as an optocoupler or a signal transformer, adding undesirable expense and complexity to the power circuit.
Accordingly, there is a need for a method and apparatus for transmitting a signal through a power magnetic structure that provides for isolating control or other signals in power magnetic circuitry without the expense and complexity of employing an additional isolation device.
The method and apparatus for transmitting a signal through a power magnetic structure of the present invention solves the aforementioned problems and meets the aforementioned needs by providing a power magnetic core having one or more windings for transmitting power, and two windings for transmitting a signal or auxiliary power. The signal or auxiliary power windings are looped around features of the core so as to cancel the effect of magnetic flux circulating in the core as a result of currents flowing through the one or more power windings.
Preferably, the magnetic core has at least two apertures defining a center portion between the apertures and two leg portions. The core has primary and secondary windings as is typical in the art. Magnetic flux produced in the core by the primary for linking the secondary circulates through one of the leg portions in either the right hand or left hand sense, and circulates through the other leg portion in the opposite sense.
To transmit a signal, an input signal winding has a first portion looped around one of the leg portions so that an input signal current passed through the first winding will produce a magnetic flux in that leg portion that circulates in either the right hand or left hand sense. A second portion of the input signal winding is looped around the other leg portion in the opposite sense.
To provide an output, an output signal winding has a first portion looped around one of the leg portions in either. the right hand or left hand sense, and a second portion looped around the other leg portion in the opposite sense. A signal or power may be transmitted through power magnetic structure simultaneously with use of the magnetic structure as a component of a main power train.
Therefore, it is a principal object of the present invention to provide a novel method and apparatus for transmitting a signal through a power magnetic structure.
It is another object of the present invention to provide a method and apparatus for transmitting a signal through a power magnetic structure that provides for isolating the output of the signal from the input of the signal.
It is still another object of the present invention to provide such a method and apparatus for transmitting a signal through a power magnetic structure that provides for decreased cost.
It is yet another object of the present invention to provide such a method and apparatus for transmitting a signal through a power magnetic structure that provides for decreased circuit complexity.